The present invention relates to baseband systems and, more particularly, to a method and apparatus for adding tagging to the signals from the down converters of a baseband system such that the converter unit can be operated on all channels simultaneously.
A prior art baseband system is shown in FIG. 1 in simplified form. For convenience and simplicity, only two channels are shown. The system, generally indicated as 10, comprises a first channel, generally indicated as 12, and a second channel, generally indicated as 14. The first channel 12 has a mixer 16 receiving RF signals in the 10-14 GHz range on input line 18, which signals are mixed with an 18 GHz signal from local oscillator 20. The resulting output signal from the first channel down converter 12 appears on line 22. The second channel down converter 14 operates in a similar manner, mixing 14-18 GHz signals on input line 24 with a 22 GHz signal from local oscillator 26 at mixer 28. The output from mixer 28 appears on line 30. The outputs on lines 22 and 30 pass through sequencing switch 32 which is automatically sequenced between the lines 22, 30 by switch driver 34. In a typical system with more channels of down conversion, the switch driver 34 would sequence switch 32 between the output lines from the various down converters. The output from switch 32 is the input to the single 4-8 GHz receiver 36. As will be understood, in a system such as system 10 of FIG. 1, it was necessary to continually sequence through the various converter bands in order to determine if a signal was present so that complete frequency identification could occur. The result of this approach, of course, is a low mean time to intercept and a low probability of intercept.
Wherefore, it is the object of the present invention to provide a baseband conversion system wherein the mean time to intercept is minimized and the probability of intercept is maximized.